Low temperature, moderate pressure fusing is a toner fusing methodology by exploiting a regime of applied pressures and temperatures to produce a high image quality output. This enables use of robust, long life subsystem components and reduced toner design complexity. The toner fusing methodology includes a multi-step, toner fusing process, in which the toner material is first softened on the print substrate. The softened toner layer is then subjected to a low temperature, moderate pressure nip to flow the softened toner layer to insure adequate coalescence and adhesion to the print substrate. By performing this toner fuse process as a multi-step process at low temperatures, burdens placed on the fusing subsystem components and the toner material design are alleviated.
As shown in FIG. 1, the low temperature, moderate pressure fusing process includes first pre-heating a print substrate 12 with unfused toner particles 14 thereon, and then forming a pressure nip between a fuser roll 10 and a pressure roll 30 in order to fuse the unfused toner particles 14 onto the print substrate 12.
The toner softening step may be practiced in various manners including chemical, mechanical, thermal, or other means to invoke a viscoelastic toner softening. For example, toner softening has been achieved by heating the toner layer through a non-contact warming zone using a radiant heating device. As a result, the toner/substrate interface is heated to temperatures above the glass transition temperature or melting temperature of the toner, softening the toner material. The softened toner image is then passed through a robust pressure nip region to coalesce the toner image and to insure adequate adhesion to the substrate. Conventional pressure nip is formed between an anodized aluminum roll 10 and a polyurethane pressure roll 30, with the toner contacting surface operated at the same or similar surface temperature to that of the heated/softened toner layer.
However, as known in the art, toner materials have high adhesion to Al surfaces that result in substantial toner offset (see 25 in FIG. 1) to the Al surface of the fuser roll 10 during the fusing process.
Conventional solutions to solve this toner offset problem include applying a release agent or oil to the Al roll surface to facilitate toner release as shown in FIG. 1. For example, a release management subsystem 40 is used to apply the release layer. Specifically, the release management subsystem 40 includes a sump 20 containing a polymeric release agent 22 which may be a solid or liquid at room temperature, but is a fluid at operating temperatures. For applying the polymeric release agent 22 to the outer surface of the fuser roll 10, two release agent delivery rolls 17 and 19 are rotatably mounted in a direction to transport release agent 22 from the sump 20 to the fuser surface. As illustrated in FIG. 1, roll 17 is partly immersed in the sump 20 and transports the release agent from the sump to the delivery roll 19. By using a metering blade 24, a layer of polymeric release oil can be applied initially to the delivery roll 19 and subsequently to the outer surface of the fuser roll 10 in a controlled thickness of about 0.1 to 2 micrometers, or greater.
However, even with the release layer, toner offset to Al surfaces still occurs at temperatures near the operating set-points. In fact, significant toner offset to the Al surfaces is observed for both wax-containing toner materials and wax-less toner materials.
Thus, there is a need to overcome these and other problems of the prior art and to provide low adhesion materials useful for fixing members.